Hitherto known circular looms, in which inner and outer partial healds were disposed circularly in two rows around a main shaft of the loom, and moved up and down by means of two rows of control levers by a plate cam rotating with the main shaft of the loom, are provided with only one row of stationary partial healds for the reduction of the moved elements of the change of shed means, each having a plurality of inner and outer yarn eyes for the warp threads, which are fastened in pairs on the strands by endless strings or band means. The endless strings of the respective groups on each partial heald are guided together or individually around two rollers, which are spaced apart from each other. Here, all inner strings of the strands are fastened at their lower regions onto a vertical slide, which is moved up and down by scanner rollers and a cam on the plate cam, whereby a countercurrent up-and-down alternating motion is conveyed onto the endless strings and hence onto the yarn guiding eyes, thus forming the travelling shed.
By means of the reduction of the partial heald means to a "single-row" construction, the number of moved control components have been able to be substantially reduced, whereby new difficulties have arisen, as, in particular, the fact that the vertical slide tends to cant and, thereby, to jam, owing to the effect of the high radial and tangential force thereon from the scanner rollers coming from the cam, which can only be controlled by considerable equipment.